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Blood Testing for Allergies

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Pros and Cons of Allergy Blood Tests

Advantages of allergy blood tests include:

  • Can be done at any time, regardless of any medications you are taking.
  • Requires only one needle stick (unlike skin testing). This may be more attractive for people who are afraid of needles. Allergy blood testing is the preferred test for infants and very young children.

Disadvantages of allergy blood tests include:

  • More expensive than skin testing. Many health insurers do not cover allergy blood tests.
  • May be less sensitive than skin tests.
  • Takes days or weeks to get results because the blood sample must be sent to a laboratory for evaluation. Skin testing provides immediate results.

Allergy Blood Test Results

A positive result means allergy-specific antibodies were detected in your blood. This is usually a sign of an allergy.

The blood test will reveal what exactly you are allergic to. However, you can test positive for something but never have had an allergic reaction to it.

A negative result means you probably do not have a true allergy. That means your immune system probably does not respond to the allergen tested. However, it is possible to have a normal (negative) allergy blood test result and still have an allergy.

Allergy blood test results should be interpreted with caution by an allergy specialist. Your doctor will also consider your symptoms and medical history when diagnosing a specific allergy.

Side Effects of Allergy Blood Tests

Allergy blood testing is relatively safe. Side effects are usually minor and may include:

  • Swelling and redness at the site where the needle was inserted
  • Pain
  • Bleeding at the site where the needle was inserted
  • Some people may faint during blood testing.

WebMD Medical Reference

Reviewed by Melinda Ratini, DO, MS on November 19, 2013
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